Valves which have a remote actuator incorporated into its design and a manual override device, commonly referred to as a manual opening jack, to allow manual operation of the valve in the event of a power failure are well known in the art. Likewise, it is well known in the art to incorporate devices which are designed to override a manual opening jack to allow a valve so equipped to move to its normal position in the event of fire. Examples of such devices are disclosed in U.S. Pat. Nos. 4,421,134, 4,240,455, and 4,505,291. The major drawback of these designs is that the heat responsive mechanism must be incorporated into the manual opening jack at the time of manufacture. Thus, if it becomes desirable to place a valve incorporating such features into service after the valve has been installed in a conduit or pipe, it becomes necessary to remove the pipe section involved from service and change out the entire valve assembly.
It is also well known in the art to equip a remote valve actuator with a fire or heat sensitive lockout cap which, when fitted to the actuator, locks the valve in an actuated position, and, in response to a high heat situation such as a fire, releases the actuation mechanism to allow the valve to move into its normal position. Examples of such lockout caps are disclosed in U.S. Pat. Nos. 3,771,540, 3,838,705, 3,842,853, 3,896,835, 4,214,600, 4,245,662, and 4,271,857.
Of course, the disadvantage of such lockout caps is that valves so equipped are not operational while the cap is in place so that the function of such valves is limited to fire safety.